EP3488628A1 - Method and system for orthogonal multi-protocol transmissions - Google Patents
Method and system for orthogonal multi-protocol transmissionsInfo
- Publication number
- EP3488628A1 EP3488628A1 EP16767021.5A EP16767021A EP3488628A1 EP 3488628 A1 EP3488628 A1 EP 3488628A1 EP 16767021 A EP16767021 A EP 16767021A EP 3488628 A1 EP3488628 A1 EP 3488628A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- ofdm
- subcarriers
- signal
- lte
- ofdm signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0037—Inter-user or inter-terminal allocation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/14—Spectrum sharing arrangements between different networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
- H04L27/26025—Numerology, i.e. varying one or more of symbol duration, subcarrier spacing, Fourier transform size, sampling rate or down-clocking
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
- H04L27/2603—Signal structure ensuring backward compatibility with legacy system
Definitions
- the present disclosure relates to wireless communication systems and in particular a method and system for orthogonal multi-protocol transmissions in wireless communication networks.
- OFDM Orthogonal frequency-division multiplexing
- DSL Digital Subscriber Loop
- ADSL Asymmetric DSL
- VDSL Very-high-bit-rate DSL
- POTS Plain Old Telephone Service
- DVB Digital Video Broadcasting
- PLC Power Line Communications
- ITU-T G.hn for home wiring LANs, telephone modems, DOCSIS - Data Over Cable System Interface Specification for broadband delivery, MoCA - Multimedia Over Coax Alliance home networking, and wireless communications including I EEE 802.1 1 (e.g. Wi-Fi), H I PERLAN , Digital TV, Personal Area Networks (PAN), and Ultra-Wdeband (UWB) Networks.
- I EEE 802.1 1 e.g. Wi-Fi
- H I PERLAN Digital TV
- PAN Personal Area Networks
- UWB Ultra-Wdeband
- OFDM and its multiple access variant OFDMA continue to find increasing applications, for example in 3 rd Generation Partnership Project (3GPP)-based wireless networks such as Long Term Evolution (LTE) and Evolved Universal Mobile Telecommunications System Terrestrial Radio Access (E-UTRA) networks, but also in I EEE-based networks such as Mobile Broadband Wreless Access (MBWA, also referred to as I EEE 802.20).
- 3GPP 3rd Generation Partnership Project
- LTE Long Term Evolution
- E-UTRA Evolved Universal Mobile Telecommunications System Terrestrial Radio Access
- I EEE-based networks such as Mobile Broadband Wreless Access (MBWA, also referred to as I EEE 802.20.
- Next Generation mobile networks are planning to use OFDM as the platform for this new and exciting product evolution, and even the Wreless Gigabit Alliance (WiGig) plans to use OFDM in the 60 GHz frequency band to enable conference room cell sizes to achieve 100 Gigabits per second (Gbps) data rates.
- WiGig Wi
- OFDM is a digital modulation technique that uses frequency division multiplexing to create multiple orthogonal sub-carriers to carry parallel data streams.
- Sub-carriers are modulated using conventional modulation schemes such as Binary Phase Shift Keying (BPSK) or Quadrature Amplitude Modulation (QAM) with defined symbol rates enabling multiple parallel data streams to be carried.
- BPSK Binary Phase Shift Keying
- QAM Quadrature Amplitude Modulation
- Wi-Fi employs short 3.2
- microsecond ( ⁇ ) symbols with 0.4 or 0.8 ⁇ for the cyclic prefix
- 52 carriers spaced at 312.5 kHz to create a high speed data channel capable of withstanding the low dispersion experienced in short reach indoor channels which Wi-Fi APs typically address
- LTE typically employs longer 66.7 ⁇ symbols (or 71 .4 ⁇ with the cyclic prefix) with 15 kHz spaced subcarriers to address significant inter-symbol interference issues typical of long reach outdoor cellular channels.
- Implementations differ by symbol time and sub-carrier spacing, but also by many other physical layer parameters including the number of sub-carriers, channel spacing, Fast Fourier Transform (FFT) size, number and operation of pilot tones, convolutional codes employed, Forward Error Correction (FEC) design, sub-carrier modulation schemes, time-interleaving, equalizer operation, and Multiple-Input Multiple-Output (M IMO) operation to name a few.
- FFT Fast Fourier Transform
- FEC Forward Error Correction
- M IMO Multiple-Input Multiple-Output
- LAA- LTE License Assisted Access for Long Term Evolution
- LAA License Assisted Access for Long Term Evolution
- LBT Listen Before Talk
- RF Radio Frequency
- Wi-Fi operates asynchronously by applying the etiquette rules and sending / receiving packets when the medium is free.
- 3GPP operates synchronously and employs advanced scheduling algorithms to maximize channel utilization, and therefore is not burdened with etiquette rules. As a result, 3GPP is able to carry higher traffic loads efficiently i.e. in a way that maximizes the use of the valuable frequency channel resources.
- 3GPP-based technologies are not currently designed to support a sharing etiquette, such as that which W-Fi supports.
- One such proposal includes implementing a power-based LBT detect threshold. Wth this proposal, the LTE radio would monitor energy on the channel and consider it free if the received signal strength indication (e.g. RSSI) is lower than that threshold. However, this proposal does not address the variability of cell sizes due to unlicensed band interference. Also, in some implementations, the threshold is fairly large (-62 dBm) and limits the cell size. Depending on the channel conditions, there is no guarantee that the LTE radio will detect a transmitted signal above the threshold and this ultimately may result in a higher collision count and lower throughput.
- an OFDM transmitter is configured to generate transmissions associated with one OFDM technology or protocol (OFDM2) using subcarriers of another OFDM technology (OFDM 1).
- multi-protocol transmissions as described herein may be performed sequentially (e.g. in a time division multiplexing fashion) or concurrently (e.g. during the same or an overlapping time interval).
- an OFDM 1 transmitter may be configured to map or assign the different OFDM signals to different subsets of the available OFDM 1 subcarriers such that the data contained therein can be transmitted at the same or during an overlapping time.
- an OFDM 1 transmitter may be configured to assign different subsets of the OFDM 1 subcarriers to simultaneously or concurrently transmit OFDM 1 and OFDM2 information.
- an LTE transmitter uses a first subset of LTE subcarriers to generate and transmit an LTE signal that can be understood by LTE receivers, for example, a Discovery Reference Signal (DRS) for License Assisted Access for Long Term Evolution (LAA-LTE or LAA).
- DRS Discovery Reference Signal
- LAA-LTE or LAA License Assisted Access for Long Term Evolution
- the LTE transmitter uses a second, different subset of LTE subcarriers to generate and transmit another LTE signal carrying 802.1 1 (e.g.
- Wi-Fi Wi-Fi information that can be understood by Wi-Fi receivers, for example, to reserve the channel for a certain duration, to indicate a transmission time associated with an on-going and/or upcoming LTE transmission or to create a carrier sense indication, for example, to cause Wi-Fi receivers and other radio technologies to consider the channel as busy.
- an OFDM 1 transmitter may, in other implementations, use OFDM 1 subcarriers which are located in unused portions of the OFDM2 system bandwidth, and hence orthogonal to subcarriers in the used portion in the OFDM2 system bandwidth.
- an LTE transmitter can be configured to generate and/or transmit LTE information using LTE subcarriers located in unused portion(s) of the Wi-Fi system bandwidth independently of or in addition to transmitting W-Fi or LTE information using LTE subcarriers located in portions of the W-Fi system bandwidth normally used or occupied by W-Fi subcarriers.
- LTE LTE information using LTE subcarriers located in unused portion(s) of the Wi-Fi system bandwidth independently of or in addition to transmitting W-Fi or LTE information using LTE subcarriers located in portions of the W-Fi system bandwidth normally used or occupied by W-Fi subcarriers.
- an LTE transmitter operating in the same or an overlapping system bandwidth can advantageously generate and transmit additional LTE data using subcarriers orthogonal to those normally used in the underlying W-Fi channel.
- the LTE transmitter can limit its LTE transmissions to only use the LTE subcarriers in non-utilized portion(s) of the W- Fi system bandwidth.
- the LTE transmitter can be configured to transmit LTE and W-Fi signals concurrently (by partitioning the LTE available subcarriers into subsets) or in sequence (e.g. by using the LTE subcarriers to generate and/or transmit a W-Fi signal to reserve the channel for a subsequent LTE transmission).
- the embodiments described are primarily in relation to the generation and transmission of W-Fi and LTE information using LTE subcarriers. However, the same approach is equally applicable to other OFDM technologies such as for example 802.15 technologies (e.g. ZigBee). Generally, the principles described herein are applicable to any implementation where subcarriers or symbol information from one OFDM technology are used to transmit subcarrier or symbol information using subcarriers of another OFDM technology. In some
- the principles described herein are applicable to generate any possible signal to the extent allowed by the spectral bandwidth available to the OFDM transmitter.
- the principles are equally applicable to other non- OFDM technologies or to generate non-OFDM signals.
- the principles described herein may be employed to generate I EEE 802.1 1 b CCK signals, using subcarriers or symbol information from one OFDM technology.
- the principles described within may even be applied to signal generation for applications yet undetermined, a possible example being in-building "radar", using specialized signals to detect and characterize in-building objects for the purpose of high precision location tracking.
- a method for an OFDM transmitter or transmitting node configured for OFDM signal transmissions is provided.
- the method includes generating a first OFDM signal containing data associated with a first OFDM communication protocol, where the first OFDM communication protocol is defined to use a first system bandwidth that overlaps with a second system bandwidth associated with a second OFDM communication protocol.
- the method further includes transmitting the first OFDM signal over a non-utilized portion of the second system bandwidth.
- the first OFDM signal is transmitted using a first subset of a first plurality of subcarriers having a first subcarrier frequency spacing, where the first subset is located in the non-utilized portion of the second system bandwidth.
- the method further includes generating a second OFDM signal containing data associated with the second OFDM communication protocol, and transmitting the second OFDM signal over the second system bandwidth.
- the first and second OFDM signals are transmitted at a same or a different time.
- transmitting the first OFDM signal includes transmitting the first OFDM signal over the non-utilized portion of the second system bandwidth if another transmission is in progress in the second system bandwidth.
- the method further includes, prior to transmitting the first OFDM signal, transmitting the second OFDM signal over the second system bandwidth, where the second OFDM signal is indicative of one of a transmission length, transmission time, transmission type and a channel reservation time associated with at least one of the first and second OFDM signals, and where the first OFDM signal is subsequently transmitted over the second system bandwidth.
- the second OFDM signal is transmitted using a second plurality of subcarriers having a second subcarrier frequency spacing different than the first subcarrier frequency spacing, where the second plurality of subcarriers is located in a utilized portion of the second system bandwidth.
- the second OFDM signal is transmitted using a second subset of subcarriers from the first plurality of subcarriers, different from the first subset, where the second subset being located in the utilized portion of the second system bandwidth.
- the first and second OFDM signals are generated in one of a time domain and a frequency domain, based on respective first and second predetermined OFDM signals containing data associated with the first and second OFDM communication protocols.
- generating the first OFDM signal includes mapping the first predetermined OFDM signal to subcarriers in at least the first subset and where generating the second OFDM signal includes mapping the second predetermined OFDM signal to subcarriers in at least the second subset.
- the second subset includes at least one subcarrier overlapping in frequency with a subcarrier of the second plurality of subcarriers.
- generating the second OFDM signal further includes generating the second predetermined OFDM signal, and interpolating the second predetermined OFDM signal generated using the first plurality of subcarriers to produce an interpolated OFDM signal that can be mapped to subcarriers in the second subset.
- the first OFDM communication protocol includes an LTE protocol and the second OFDM communication protocol includes an 802.1 1 protocol.
- the first OFDM signal includes an LTE signal and the second OFDM signal includes one of a Clear To Send (CTS) frame, a Short Training Field (STF), a Long Training Field (LTF), and a Signal Field (SIG).
- CTS Clear To Send
- STF Short Training Field
- LTF Long Training Field
- SIG Signal Field
- the first OFDM signal is transmitted at a power level different than a power level for the second OFDM signal.
- an OFDM transmitter or transmitting node configured for OFDM signal transmissions.
- the OFDM transmitter includes circuitry containing instructions which, when executed, are configured to cause the transmitter to perform any of the method embodiments described above.
- a non-transitory computer readable memory configured to store executable instructions for an OFDM transmitter or transmitting node configured for OFDM signal transmissions.
- the executable instructions when executed by a processor are configured to cause the OFDM transmitter to perform any of the method embodiments described above.
- FIG. 1 illustrates one example of a Long Term Evolution (LTE) Radio Access Network (RAN) and Wireless Local Area Networks (WLANs) configured to share unlicensed spectrum resources, in accordance with the principles described herein;
- LTE Long Term Evolution
- RAN Radio Access Network
- WLANs Wireless Local Area Networks
- FIGS. 2A-B illustrate an example of LTE subcarriers and W-Fi subcarriers used in the LTE RAN and WLANs of Figure 1 , in accordance with the principles described herein;
- FIG. 3 illustrates a timing diagram showing an example of W-Fi symbols transmitted by an LTE node in the LTE RAN of Figure 1 , in accordance with the principles described herein;
- FIGS. 4A-B illustrate timing diagram examples of W-Fi transmissions by an LTE node in the LTE RAN of Figure 1 for channel reservation in an unlicensed band in accordance with the principles described herein;
- FIG. 5 illustrates a format example for the CTS- To-Self packet of Figure 4A in accordance with the principles described herein;
- FIGS. 6A-B illustrate format examples for the Wi-Fi header transmission shown in Figure 4B in accordance with the principles described herein;
- FIGS. 7A-B illustrate the partitioning of OFDM subcarriers into two subsets for generating and/or transmitting OFDM signals of different types in accordance with the principles described herein;
- FIG. 8 illustrates an example frequency diagram of a 20 MHz W-Fi channel system bandwidth that includes portions not utilized by W-Fi subcarriers
- FIGS 9A-D illustrate frequency diagram examples of LTE subcarriers located in non-utilized portions of the Wi-Fi 20 MHz channel system bandwidth which can be used to generate and/or transmit LTE signals;
- FIGS 10A-B illustrate block diagram examples of an OFDM transmitter configured in accordance with the principles described herein;
- FIG. 1 1 illustrates a block diagram example for the signal generator and time-domain interpolator of the OFDM transmitter shown in Figure 10A, configured in accordance with the principles described herein;
- FIG. 12 illustrates a block diagram example for the frequency-domain interpolator of the OFDM transmitter shown in Figure 10B, configured in accordance with the principles described herein;
- FIGS 13A-B show a flow chart of example methods for the OFDM transmitters of Figures 10A-B in accordance with the principles described herein;
- FIGS. 14A-B show a flow chart of other example methods for the OFDM transmitters of Figures 10A-B in accordance with the principles described herein;
- FIGS 15A-B show a block diagram of exemplary embodiments of OFDM transmitting and receiving nodes configured in accordance with principles described herein, and
- FIGS 16A-B show a block diagram of other exemplary embodiments of OFDM transmitting and receiving nodes configured in accordance with the principles described herein.
- the present disclosure is directed to methods and systems for multiprotocol transmissions in shared spectrum e.g. unlicensed bands or band normally used for unlicensed access.
- the principles described herein are applicable to generating subcarriers or symbol information associated with one OFDM technology using another OFDM technology.
- an OFDM transmitter uses this approach to map or assign different subsets of the available OFDM subcarriers to different OFDM signals (signals associated with different OFDM protocols) in a way that the data contained in the signals can be transmitted at the same or during an overlapping time interval.
- This approach may be useful in implementations where different OFDM signals (e.g. an LTE Discovery Reference Signal (DRS) and an 802.1 1 signal) need to be sent to different OFDM receivers (e.g. LTE and Wi-Fi receivers) at the same time.
- DRS LTE Discovery Reference Signal
- 802.1 1 signal OFDM receivers
- LAA License Assisted Access
- LTE Long Term Evolution
- RAN Radio Access Network
- the first OFDM network may also include other 3 rd
- 3GPP Generation Partnership Project
- the first OFDM network may include any current or future wireless network infrastructure configured to generate subcarriers or symbol information associated with a different OFDM technology, with or without a licensed anchor band (so called "standalone" or single carrier access network).
- the second OFDM net ork(s) described herein primarily as WLANs may also include other types of 802 networks such as a Wreless Personal Area Networks (WPAN) or a Wreless Metropolitan Area Networks (WMAN).
- the second OFDM network(s) may also include wireless networks that use a different OFDM technology such as for example 802.15 networks (e.g. ZigBee). More generally, the second wireless network(s) may include any OFDM network that uses a subcarrier spacing equal to or greater than the subcarrier spacing used in the first OFDM network.
- OFDM networks which are variations of the OFDM technology used in the first OFDM network but with a greater subcarrier spacing (e.g. a second LTE network with a subcarrier spacing greater than the carrier spacing of a first LTE network).
- a second LTE network with a subcarrier spacing greater than the carrier spacing of a first LTE network.
- WLAN or Wi-Fi is used to cover all of these possibilities for the second OFDM network(s).
- an LAA-LTE RAN 10 an example of the first OFDM network
- an access node 60 is configured to transmit subcarrier and/or symbol information which can be detected by wireless devices 50, 52, 54, 56, 58 operating in WLANs 20, 30 (examples of a second OFDM network).
- the unlicensed band is used to operate a (secondary) carrier to add capacity to a (primary) carrier operating in licensed spectrum (e.g. an LTE carrier). Operation of the primary licensed carrier may be under the control of the access node 60 or another node in the LAA-LTE RAN 10.
- the access node 60 is an eNodeB but in other implementations, the access node 60 may be a Node B (NB), evolved Node B (eNB), base station, base station controller (BSC), radio network controller (RNC), relay, donor node controlling relay, base transceiver station (BTS), transmission point, transmission node, remote RF unit (RRU), remote radio head (RRH), a node in a distributed antenna system (DAS), or a memory management unit (MMU).
- NB Node B
- eNB evolved Node B
- BSC base station controller
- RNC radio network controller
- relay donor node controlling relay
- BTS base transceiver station
- RRU remote RF unit
- RRH remote radio head
- DAS distributed antenna system
- MMU memory management unit
- the access node 60 is configured to control transmissions to or from UEs in the LTE RAN 10 but other nodes in the LTE RAN 10, a Core Network (CN
- an Internet Protocol (IP) node in an IP network may be configured for that purpose.
- a wireless device or UE for example, a relay node UE
- devices that use a different OFDM technology e.g. devices in the WLANs 20, 30.
- the functionality described herein in relation to nodes that are configured to transmit such subcarrier or symbol information in a wireless network may also equally apply to wireless devices (e.g. UEs) configured as such.
- the access node 60 provides wireless devices within its coverage (e.g. devices 40, 50) with access to network services in one more core networks 70, in this example, an Evolved Packet Core (EPC) network which includes a Mobility Management Entity 74 and a Packet Data Network (PDN) Gateway (PGW) 72.
- EPC Evolved Packet Core
- PDN Packet Data Network Gateway
- Each wireless device 40, 50 is configured for wireless communication in the LAA-LTE RAN 10 (e.g.
- UE User Equipment
- UE User Equipment
- a wireless terminal also known as a mobile station, a mobile phone ("cellular" phone), a desktop, laptop, netbook, and/or tablet computer, a laptop embedded equipment (LEE), laptop mounted equipment (LME), or a portable device such as an e-book reader, watch, digital music and/or video player, camera, game controller and/or device but also may be a computing- like device such as a heart monitoring implant, biochip transponder, automobile, sensor, modem, thermostat, and/or other home or car appliance generally referred to as an internet of Things (ioT) device, a machine type communication (MTC) device (also known as a machine-to-machine (M2M) or device-to-device (D2D) device.
- ioT internet of Things
- MTC machine type communication
- M2M machine-to-machine
- D2D device-to-device
- the LAA-LTE RAN 10 shares the unlicensed band with WLANs 20, 30 for transmissions involving at least some of the wireless devices in its coverage (e.g. wireless device 50).
- the WLANs 20, 30 may each include any number of wireless devices communicating directly or via an Access Point (AP) with other devices in the same or different networks, in the example of Figure 1 , WLAN 20 is shown to include WLAN devices 52, 54, AP 58 as well as wireless device 50 while WLAN 30 includes WLAN devices 54 and 56.
- Other network configurations for WLANs 20, 30 or other types of networks or devices which may share unlicensed spectrum resources with device 50 in the LAA-LTE RAN 10 are possible.
- devices 50, 52, 54 and AP 58 in WLAN 20 and devices 54, 56 in WLAN 30 are configured to share a band of spectrum using some form of media access method and/or transmissions based on contention.
- WLAN or Wi-Fi devices are configured to share a band of spectrum using some form of media access method and/or transmissions based on contention.
- contention-based approaches include Listen- Before-Talk (LBT), Carrier Sense Multiple Access (CSMA) - with Collision
- CSMA-CD CSMA with Collision Avoidance
- CSMA- CA CSMA with Collision Avoidance
- a WLAN device 50, 52, 54, 56, 58 will try to determine whether another transmission is in progress in the channel or band used. This determination may be based on the detection of a carrier wave, signal or energy in the channel of interest. If a carrier or energy is detected in the channel of interest (in another fully or partially overlapping channel), the WLAN device 50, 52, 54, waits for the transmission in progress to finish before initiating its own
- the LAA-LTE RAN 10 may include wireless devices 40 in a location outside the coverage of WLANs 20, 30, and with which spectrum resources are not shared.
- the wireless devices 40, 50 described in the embodiments herein may (but do not need to) be configured for operation on multiple different wireless networks.
- wireless device 50 is configured as a dual-mode device (i.e. configured as a UE for operation in the LAA-LTE RAN 10 as well as a WLAN device for operation in WLANs 20, 30) while wireless device 40 is configured as a UE for operation in the LAA-LTE RAN 10 only.
- the principles of the present disclosure apply whether or not wireless devices 40, 50 in the LAA-LTE RAN 10 are configured as single-mode or multi-mode devices.
- 3GPP systems such as the LAA-LTE RAN 10 of Figure 1 typically operate outdoors, usually from high powered macros cell sites designed to cover ranges up to several kilometers.
- the resulting coherence bandwidth of the channel is very small as the delay spread (i.e. the impulse response of the channel) can be quite large due to distant reflections from building and other environmental factors.
- 3GPP systems break the available bandwidth into many narrower sub-carriers or sub-channels and transmit the data in parallel streams.
- Figure 2A shows a time-frequency diagram 80 of a set of LTE sub-channels (only a subset shown) used in a channel of the LTE RAN 10 of Figure 1.
- each LTE subcarrier L-SCI-M is modulated using varying levels of QAM modulation, e.g. QPSK, QAM, 64QAM or possibly higher orders depending on signal quality.
- QAM modulation e.g. QPSK, QAM, 64QAM or possibly higher orders depending on signal quality.
- Each OFDM symbol 82 is therefore a linear combination of the instantaneous signals on each of the sub-carriers L-SCI-M in the channel. Because data is transmitted in parallel rather than serially, LTE symbols 82 are generally much longer than symbols on single carrier systems of equivalent data rate.
- each LTE symbol 82 is 66.7 microseconds ( ⁇ ) long and is preceded by a 4.7 ⁇ cyclic prefix (CP) (not shown), which is used to reduce Inter-symbol Interference (ISI).
- CP cyclic prefix
- the total symbol length (including the CP) is 71.4 [is.
- Wi-Fi systems operate (mostly) indoors, usually from low power APs designed to cover ranges up to 50 or 100 meters.
- the resulting coherence bandwidth of the channel is large, as the delay spread (e.g. the impulse response of the channel) is usually very short, typically less than 500 nanoseconds (ns).
- W-Fi systems use wider 312.5 KHz subchannels.
- Figure 2B shows a time-frequency diagram 90 of a set of W-Fi subchannels (only a subset shown) used in a channel of the WLANs 20, 30 of Figure 1.
- CP 0.8 ⁇ cyclic prefix
- M is the number of OFDM1 subcarriers
- N is the number of OFDM2 subcarriers.
- an OFDM1 transmitter is configured to generate and transmit subcarrier and/or symbol information of any OFDM2 system that uses a subcarrier spacing larger (or substantially larger, e.g. by a factor of 10 or 20) than the OFDM 1 subcarrier spacing.
- the OFDM 1 transmitter is configured to generate and transmit subcarrier and/or symbol information of any OFDM2 system that uses a symbol duration smaller (or substantially smaller, e.g. by a factor of 10 or 20) than the OFDM1 symbol duration.
- the LTE subcarrier spacing is smaller than the W-Fi subcarrier spacing (which means the Wi-Fi symbol duration is smaller than the LTE symbol duration).
- the OFDM1 transmitter is configured to generate and transmit subcarrier and/or symbol information of any OFDM2 system that has a system bandwidth that is greater or equal to the OFDM 1 system bandwidth.
- this may not be necessary.
- LTE can operate at multiple different system bandwidths (e.g. 5, 10, 15, 20 MHz) some of which may be smaller than the W-Fi system bandwidth
- an LTE transmitter can generally be configured to utilize the available spectrum in a way that is sufficient for W-Fi transmissions (see for example the implementations described below in relation to Figures 7A-B).
- an LTE transmitter may encode and transmit W-Fi information in a way that it can be recovered by a Wi-Fi receiver.
- the LTE transmitter may also be configured to generate subcarrier and/or symbol information of yet other OFDM technologies.
- an LTE transmitter e.g. the access node 60 of Figure 1
- LTE subcarriers L-SCI-M can use LTE subcarriers L-SCI-M to generate 802.1 1 (e.g. W-Fi) subcarrier or symbol information that can be understood by Wi-Fi receivers, for example to reserve the channel for a certain duration, to indicate a transmission time associated with an on-going and/or upcoming symbol transmission or to create a carrier sense indication, for example, to cause Wi-Fi receivers and other radio technologies to consider the channel as busy.
- 802.1 1 e.g. W-Fi subcarrier or symbol information that can be understood by Wi-Fi receivers, for example to reserve the channel for a certain duration, to indicate a transmission time associated with an on-going and/or upcoming symbol transmission or to create a carrier sense indication, for example, to cause Wi-Fi receivers and other radio technologies to consider the channel as busy.
- the embodiments described below are primarily in relation to the generation of W-Fi subcarriers / symbol
- OFDM technologies such as for example 802.15 technologies (e.g. ZigBee).
- 802.15 technologies e.g. ZigBee
- the principles described herein are applicable to generating subcarriers or symbol information from one OFDM technology using another OFDM technology.
- FIG. 3 illustrates a timing diagram 100 showing an example of a symbol transmission by an LTE transmitting node (e.g. the access node 60 in the LTE RAN 10 of Figure 1), in accordance with the principles described herein.
- the access node 60 is configured to transmit W-Fi information, for example W-Fi header and/or packet data to indicate its current use of a
- each W-Fi symbol 1 10, 1 12, 1 14 includes a respective CP 1 10a, 1 12a, 1 14a (e.g. 0.8 ⁇ ) and has a symbol duration (e.g. 3.2 ⁇ ) that conforms to the duration expected by devices in the WLANs 20, 30.
- the number of W-Fi symbols 1 10, 1 12, 1 14 is designed to fit into one LTE symbol duration 102 (e.g. after an LTE symbol preamble or CP 102a) but in other implementations, the number of W-Fi symbols 1 10, 1 12, 1 14 is substantially less than one LTE symbol duration 102. In yet other implementations, the number of W-Fi symbols 1 10, 1 12, 1 14 is substantially less than one LTE symbol duration 102. In yet other
- the access node 60 uses up to sixteen W-Fi symbols 1 10, 1 12, 1 14 in a 66.7 ⁇ LTE symbol time duration. In yet other implementations, the access node 60 uses some of the W-Fi symbols 1 10, 1 12, 1 14 for W-Fi header data and the rest for W-Fi packet or frame data, the size of which depends on the W-Fi modulation rate used. In yet other implementations, the W-Fi symbols 1 10, 1 12, 1 14 are organized in multiple sets to span over multiple LTE symbol durations where each set is configured to fit in the duration of one LTE symbol. In yet other implementations, the first Wi-Fi symbol set is preceded by an LTE CP (e.g.
- W-Fi symbols 1 10, 1 12, 1 14 shown in Figure 3 represent one particular type of W-Fi symbols that can be used (e.g. for W-Fi data transmissions). However, it is important to note that depending on the implementation and the type of W-Fi transmission desired, the principles described herein also equally apply to other types of W-Fi symbols. For example, short and long W-Fi symbols such as those defined for Short Training Fields (STFs) and Long Training Fields (LTFs) could be used.
- STFs Short Training Fields
- LTFs Long Training Fields
- the W-Fi symbols may or may not be transmitted with a CP and may have time duration that is different from the time duration of the W-Fi symbols 1 10, 1 12, 1 14 (e.g. other 3.2 ⁇ ). Other possibilities exist for the W-Fi symbols 1 10, 1 12, 1 14.
- the W-Fi information contained in the W-Fi symbols 1 10, 1 12, 1 14 is to reserve the channel for the LTE transmission.
- the W-Fi information may be indicative of a transmission time, length, type associated with and/or a channel reservation time necessary for transmitting the W-Fi symbols 1 10, 1 12, 1 14, the LTE symbols 104 or a combination of both.
- the access node 60 generates W-Fi symbols 1 10, 1 12, 1 14 to contain a W-Fi header or a Clear-To Send (CTS) packet such as a "CTS-to-Self packet to reserve the channel with a "virtual carrier sense", enabling devices in the WLANs 20, 30 to receive this header / packet information down to -82 dBm or lower and refrain from transmitting until after the LTE transmission (e.g. the LTE symbols 104) has been sent.
- the access node 60 can apply the same (LTE) processing functions such as filtering, PAR, digital pre-distortion, PSD
- the access node 60 may also use W-Fi symbols 1 10, 1 12, 1 14 to send PROBE REQUEST packets to detect nearby Wi- Fi APs.
- the access node 60 uses the Wi-Fi symbols 1 10, 1 12, 1 14 to send disassociation or de-authentication packets to W-Fi Stations (clients) in an attempt to move them to the LTE RAN 10.
- the access node 60 can use to Wi-Fi symbols 1 10, 1 12, 1 14 to send other types of W-Fi packets or frames including for example N ULL packets, Wi-Fi sounding packets, LWA packets, Point Coordination Function (PCF) beacons, etc.
- PCF Point Coordination Function
- FIGS 4A-B two different W-Fi transmissions 124, 134 that the access node 60 can use to reserve the channel for a subsequent LTE symbol transmission are shown.
- the LTE symbol transmission is shown as a series of Transmission Time Intervals (TTIs) 126a-d and 138a-d which, in this example, are 1 millisecond (msec) each in duration.
- TTIs Transmission Time Intervals
- 138a-d 1 millisecond (msec) each in duration.
- Each of the W-Fi transmissions 124, 134 has a duration that fits within one LTE symbol but as noted above, the W-Fi transmissions 124, 138 may span multiple LTE symbols in other implementations.
- a W-Fi CTS-to-Self packet 124 is used to reserve the channel for TTIs 126a-d (only four shown) while in the example of Figure 4B, a W-Fi header 134 is used for TTIs 138a-d.
- each of the CTS-To-Self packet 124 and header 134 contains a channel reservation indication indicating an amount of time during which the access node 60 intends to use the channel.
- the reservation indication prevents listening devices (e.g. devices in the WLANs 20, 30 that have received and demodulated the indication) to perform any transmission until the reservation time has expired.
- the channel reservation indication is a Network Allocation Vector (NAV) indication in the CTS- To-Self packet 124.
- the NAV indication is a NAV timer value defining how long the channel will be reserved.
- the NAV timer value is indicative of a time required to transmit the CTS packet, the LTE TTIs 126a-d (e.g. NAV reservation time 128) and/or a combination thereof.
- the NAV timer value is an end time of the LTE TTI 126a- d transmission.
- the devices that receive and demodulate the CTS packet will refrain from transmitting until a timer set to the NAV timer value expires.
- the channel reservation indication is included in a different field of the CTS-to-Self packet 124. Generally, any packet data or any field of a Wi-Fi packet may be used for the channel reservation indication.
- the channel reservation indication is a value indicative of any one of a transmission length, time or type or a channel reservation time associated with the CTS-to-Self packet 124, the LTE symbols and/or both. Other possibilities exist for the channel reservation indication.
- the channel reservation indication is a length reservation indication or other control data in the Wi-Fi header 134 representing an octet count associated with the LTE TTIs 138a-d.
- the length reservation indication (or control data) is a time duration required for transmitting the W-Fi header 134, the LTE TTIs 138a-d (e.g. length reservation time 140) and/or a combination thereof.
- the length reservation indication is an end time of the LTE TTI 138a-d transmission.
- the W-Fi header 134 and the LTE TTIs 138a-d may be viewed as a combined packet transmission 130 where the LTE TTIs 138a-d (and possibly other information) form the packet data payload with a length that corresponds to the length reservation indication.
- W-Fi receivers e.g. devices in WLANs 20, 30
- LTE receivers e.g. the access node 60
- LTE receivers e.g. the access node 60
- the W-Fi header may be unrecoverable.
- the W-Fi and LTE transmissions are either contiguous or non-contiguous
- the access node 60 may, in some implementations, initiate the LTE transmission immediately after completing the W-Fi transmission or alternatively, wait after a certain delay (e.g. as in Figure 4A). In other implementations such as the example shown in Figure 4B, the access node 60 transmits noise (or some RF power) during that delay to maintain the transmit power envelope and prevent W-Fi devices to assume the channel is free.
- a certain delay e.g. as in Figure 4A
- the access node 60 transmits noise (or some RF power) during that delay to maintain the transmit power envelope and prevent W-Fi devices to assume the channel is free.
- the access node 60 may continue to use the channel beyond the time duration or end time indicated by the channel reservation indication.
- the access node 60 may also be configured for an additional transmission following TTIs 126a-d or TTIs 138a-d.
- the additional transmission may be an additional set of LTE TTIs or some other transmission (e.g. a W-Fi transmission) and is contiguous with the preceding TTIs 126a-d, 138a-d to prevent W-Fi devices from transmitting during the additional transmission.
- the channel reservation indication indicates how long the channel is reserved for the LTE TTIs 126a-d, 138a-d but not for the additional transmission.
- the access node 60 performs a channel availability check using a contention-based method, for example Listen-Before- Talk (LBT) 122, 132 to determine whether another transmission is in progress in the channel or band used. This determination may be based on the detection of a carrier wave, signal or energy in the channel or band of interest (e.g. with a -62 dBm threshold). If during that time, a carrier or energy is detected in the band or channel of interest (in another fully or partially overlapping channel or band), the access node 60 waits for the transmission in progress to finish before initiating its own transmission.
- LBT Listen-Before- Talk
- the access node 60 (immediately) transmits either the CTS-To-Self packet 124 or header information 134 and completes the subsequent LTE transmission (TTIs 126a-d or 138a-d).
- FIG. 5 illustrates an example of a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) 150 that includes the CTS-To-Self packet 124 shown in Figure 4A in accordance with the principles described herein.
- the CTS-to-Self packet denoted as 170
- PLCP Service Data Unit field 156 of the PPDU 150 which also includes a preamble 152 and a header 154 (collectively herein referred to as header) as well as tail and pad fields 158, 160.
- the CTS frame 170 includes a frame control field 172 that specifies the type of frame 170 (in this case a CTS-To-Self frame), a duration field 174 to specify a NAV timer value, a Receiver Address (RA) field 176 which is set to the Transmitter Address for a CTS-To-Self packet and a Frame Check Sequence (FCS) field 178 which specifies an error-correcting code for the CTS packet 170.
- RA Receiver Address
- FCS Frame Check Sequence
- eleven Wi-Fi symbols, each 4 ⁇ in duration, are required to transmit the CTS-To-Self packet 170 (as included in a PPDU 150) for a total transmission length of 44 ⁇ which fits into a 71.4 or 83 ⁇ symbol.
- FIG. 6A illustrates an example of a format for the Wi-Fi header 134 shown in Figure 4B in accordance with the principles described herein.
- the W-Fi header 134 is a PLCP header 208 which includes a preamble 202 and a Signal field (SIG) 204 (collectively herein referred to as header data) contains a channel reservation indication (in the SIG 204) to reserve the channel for a certain period of time.
- the channel reservation indication is set in a length field 214 as an octet count which is indicative of the amount of data to follow in a data field 206.
- the channel reservation indication in the length field 214 is indicative of the time required to transmit or an end transmission time for the data (e.g. up to 5 msec).
- the data contained in the data field 206 and the PLCP header 208 are shown as a combined transmission 200 where the data field length corresponds to the channel reservation indication contained in the SIG 204.
- the PLCP header 208 and the data field 206 may be sent as two separate transmissions (e.g. non-contiguous transmissions).
- the data includes LTE symbols (e.g.
- the data may include additional or other information such as Wi-Fi symbols and/or a random transmission (e.g. noise 136).
- additional or other information such as Wi-Fi symbols and/or a random transmission (e.g. noise 136).
- the data in the data field 206 may also be followed by an additional transmission, such as an additional set of LTE TTIs or some other transmission (e.g. a W-Fi transmission).
- the SIG 204 also includes the rate field 210 that specifies a modulation rate for the data in the data field 206, a reserved field 212, a parity field 216, a tail field 218 and a service field 220.
- the tail field 218 is set to a value indicative of a type of symbols or OFDM associated with the data in the data field 206 (e.g. in this case an LTE type).
- the tail field 218 is set of a first value when LTE symbols are present in the data field 206 and a different value when non-LTE symbols (e.g. Wi-Fi symbols) are included).
- non-LTE symbols e.g. Wi-Fi symbols
- setting the tail field 218 to a value indicative of the presence of LTE symbols in the data field 206 notifies listening devices (devices configured to receive and demodulate the PLCP header 208) that the data field 206 contains symbols of a different OFDM type (e.g. LTE symbols).
- this indication is an OFDM indication and may be included in another field (other than the tail field 218 or the SIG 204) at the same or different layer.
- the OFDM indication is included in a MAC layer protocol field, such as the Frame Control Field which contains bits (e.g. bO and b1) normally used to specify an associated protocol.
- This OFDM indication may represent an OFDM type or mode or an OFDM parameter associated with the data in the data field 206 such as symbol duration, CP duration, number of subcarriers, subcarrier spacing, subcarrier modulation formats, subcarrier frequencies, etc.
- Figure 6B shows other format examples for the W-Fi header 134 shown in Figure 4B that can be used by the access node 60 to reserve a channel according to the principles described herein.
- transmission 240 includes a Legacy (L) Short Training Field (STF) 242, a Legacy (L) Long Training Field (LTF) field 244, and a Legacy (L)-SIG 246 that contains a channel reservation indication to reserve the channel for the data (e.g. LTE symbols or Wi-Fi symbols) to be transmitted in data field 248.
- STF Short Training Field
- LTF Long Training Field
- transmission 250 includes an L-STF 252, an L-LTF 254, an L-SIG 256, a High Throughput (HT)-SIG field 258, an HT-STF 260, an HT-LTF 262 and a data field 264.
- Either the L-SIG 246 or the HT-SIG 258 is configured to contain a channel reservation indication to reserve the channel for the data to be transmitted in the data field 264.
- transmission 270 includes an L-STF 272, an HT SIG 274, an
- the HT-STF 276, an HT-LTF 278 and a data field 280 is configured to contain a channel reservation indication to reserve the channel for the data to be transmitted in the data field 280.
- the data in the data field 248, 264, 280 includes LTE symbols (e.g. LTE TTIs 138a-d in Figure 4B) but in other examples, the data may include additional or other information such as W-Fi symbols and/or a random transmission (e.g. noise 136). Other possibilities exist for the data in the data field 248, 264, 280.
- the data in the data field 248, 264, 280 may also be followed by an additional transmission, such as an additional set of LTE TTIs or some other transmission (e.g. a W-Fi transmission).
- the channel reservation indication used is a length value included in a SIG field
- any control data or field in the W-Fi header 134 can be used for the channel reservation indication.
- the channel reservation indication is a value indicative of any one of a transmission length, time or type or a channel reservation time associated with the W-Fi header 134, the data in the data field LTE symbols and/or both. Other possibilities exist for the channel reservation indication.
- a W-Fi header or preamble transmission (such as the W-Fi header 134 shown in Figure 4B) spanning over one entire LTE symbol duration (e.g. 66.7 ⁇ ) may be used to reserve a channel.
- a series of 3 W-Fi headers each including a set of LTF, STF and SIG fields plus an additional STF field is used.
- the Wi-Fi headers may be preceded by an LTE symbol preamble or CP (e.g. CP 102a of Figure 3). Note that other combinations of Wi-Fi header information may be used for the transmission, including for example:
- the W-Fi header transmission described above is configured to fit within one LTE symbol time. However, depending on the application, the W-Fi header transmission may span multiple LTE symbols. Also, the W-Fi header transmission does not necessarily need to be preceded by or followed by an LTE transmission. For applications other than channel reservation for example, it may be transmitted as a stand-alone transmission.
- the access node 60 maps or assigns different subsets of the available OFDM subcarriers to the different OFDM signals in a way that the data contained therein can be transmitted at the same or during an overlapping time interval.
- Figure 7 A illustrates an example of how an OFDM 1 transmitter (e.g. the access node 60) configured to use OFDM 1 subcarriers can partition the available subcarriers, denoted here as 281 I-M, into two subsets which can then be used for generating and/or transmitting OFDM signals carrying information associated with different OFDM communication protocols at the same time.
- a first subset of OFDM 1 subcarriers 282 is used for generating and/or transmitting a first OFDM signal (e.g. a first OFDM 1 signal) containing data associated with a first OFDM communication protocol (denoted as OFDM1).
- a second subset of OFDM1 subcarriers 284 is used for generating and/or transmitting a second OFDM signal (e.g. a second OFDM1 signal) containing data associated with a second OFDM communication protocol (denoted as OFDM2) but which, conventionally, would be generated and transmitted using OFDM2 subcarriers (shown in Figure 7 A as 2861-3).
- a second OFDM signal e.g. a second OFDM1 signal
- OFDM2 subcarriers shown in Figure 7 A as 2861-3.
- an OFDM 1 transmitter can generate and/or transmit the first and second OFDM1 signals because they both use OFDM1 subcarriers.
- the first OFDM 1 signal is generated by mapping a predetermined OFDM1 signal (e.g.
- the first and second subsets 282, 284 are formed of a number of interleaved groups of contiguous OFDM1 subcarriers (four shown for the first subset (282A D) and three for the second subset (284 A-c)). However, it is important to note the other possibilities exist. For example, depending on the number of OFDM protocols to support, a different number of subsets 282, 284 may be used.
- subcarriers in each subset 282, 284 may be contiguous or non-contiguous (in frequency) and the number and/or placement of subcarriers contained in each subset 282, 284 may vary, for example, depending on the nature of the OFDM signals and/or data they contain.
- the subcarriers for the second subset 284 are selected such that there is sufficient overlap in frequency with the OFDM2 subcarriers to ensure the second OFDM1 signal carrying the OFDM2 information can be recovered by the intended OFDM2 receiver(s).
- the number of OFDM1 subcarriers overlapping with OFDM2 subcarriers may vary. In some
- the subcarriers for the second subset 284 include at least one subcarrier that overlaps in frequency with an OFDM2 subcarrier.
- each of the subcarrier groups 824A C include at least one subcarrier that overlaps with the main lobe of an OFDM2 subcarrier 2861-3.
- the second subset 282 only includes subcarriers that overlap in frequency with an OFDM2 subcarrier (or a main lobe thereof).
- the second subset 284 includes some of the OFDM 1 subcarriers that normally are part of the frequency resources defined to be used for the predetermined OFDM 1 signal but happen to overlap with an OFDM2 subcarrier (of a main lobe thereof).
- some of the OFDM 1 subcarriers defined for the predetermined OFDM 1 signal but which overlap with an OFDM2 subcarrier are not mapped or modulated with the predetermined OFDM 1 information but are used instead to transmit the OFDM2 signal containing OFDM2 information.
- the OFDM 1 subcarriers defined for the predetermined OFDM 1 signal which also happen to overlap with an OFDM2 subcarrier (or a main lobe thereof) may instead be "blanked” or “muted” i.e. not included in any of the first or second subsets 282, 284 and therefore not used for transmitting either the first or second OFDM 1 signals. All of these possibilities may be referred to as "puncturing" of the predetermined OFDM 1 signal. Other ways of puncturing the predetermined OFDM 1 signal are possible.
- FIG. 7B illustrates a more specific example where an LTE transmitter (e.g. the access node 60) configured can partition the LTE subcarriers available across the system bandwidth into two subsets, also denoted here as 282, 284, which can then be used for generating and/or transmitting a predetermined Wi-Fi signal (e.g. the CTS-to-Self packet 124 or Wi-Fi header 134 of Figure 4B) concurrently with a predetermined LTE signal (in this example a DRS signal) that may need to be transmitted within a certain time window and /or with a certain periodicity.
- a predetermined Wi-Fi signal e.g. the CTS-to-Self packet 124 or Wi-Fi header 134 of Figure 4B
- a predetermined LTE signal in this example a DRS signal
- the ability to transmit DRS and W-Fi signals at the same time may be beneficial in implementations where the W-Fi transmission overlaps in time with a required DRS transmission.
- the DRS signal which is employed for providing Radio Resource Management (RRM) functionality for LAA operation, was introduced in 3GPP (Release 12) to support secondary cell (“SCell") activation and deactivation. SCells that are not activated for any UEs may generally be turned off except for periodic DRS transmissions.
- a conventional DRS transmission is allocated predetermined or defined Resource Elements (RE) across the system bandwidth and typically includes any combination of the following signals:
- PSS/SSS Primary Synchronization / Secondary Synchronization Signals
- CRS Cell Specific Reference Symbol
- CSI-RS Channel-State Information Reference Signals
- the information carried by the DRS typically contains cell and/or PLMN identification as well as other control information that may be required for proper LAA operation e.g. to enable UEs to identify a detected cell and/or the operator of the cell.
- the DRS is transmitted in DRS occasions that may have a periodicity of 40, 80 or 160 msec. When LBT is applied to DRS transmissions, there will be some instances where the DRS cannot be transmitted periodically as it may in licensed spectrum. According to 3GPP standards, the DRS cannot exceed 1 msec in duration (i.e.
- a typical DRS transmission is defined to include CRS signals in symbols 0, 1 and 4 of slots 0 and 1 (using every 3 rd RE), PSS/SSS signals in symbols 5/6 of slot 0 (using all REs), and Non-Zero Power (NZP) -CSI- RS signals in symbols 2, 3 of slot 1 (using every 12 th RE). All other REs may be used for CSI-RS signals (ZP or NZP), and/or control (e.g. PDCCH) or user (DPSCH) transmissions.
- DMTC Discovery Measurement Timing Configuration
- the available LTE subcarriers are partitioned into two subsets, 282, 284.
- the first subset 282 includes the subcarriers necessary to transmit and generate a predetermined CRS signal (i.e. subcarriers corresponding to every 3 rd RE) while the remainder of the subcarriers are grouped into the second subset 284 and used for a Wi-Fi transmission (e.g. the CTS-to-Self packet 124 or W-Fi header 134 of Figure 4B).
- LTE subcarriers 290 that overlap in frequency with a W-Fi subcarrier 286 (or a main lobe thereof) are included in the second subset 284. In other implementations, the LTE
- the overlapping subcarriers 290 defined to be used for CRS REs 292 are not mapped or modulated with CRS information but are instead used for transmitting W-Fi information.
- the CRS REs 292 using an overlapping LTE subcarrier 290 are punctured. In some of those implementations, this may be beneficial to improve the W-Fi signal quality required, reduce the level of distortion that can be tolerated and/or improve the probability of successful detection by a W-Fi receiver. It is understood that depending on the level of distortion and/or performance degradation that can be tolerated in the CRS signal, any number of CRS REs may be punctured, not necessarily only those that might overlap with a W-Fi subcarrier.
- the CRS signal can be fully punctured if the channel is stationary or partially punctured (e.g. every second CRS RE) if the channel estimation by the UEs could be impaired if CRS is not properly detected.
- the CRS signal can be fully punctured if the coherence time of the channel (i.e. the time over which the amplitude fading is less than a defined threshold) exceeds the duration of an LTE slot (i.e. 0.5 msec) or a configurable fraction a (e.g. a value between 0 and 1 ).
- the configurable fraction a can be set by the LTE transmitter (e.g. the access node 60) or higher layer network nodes.
- some or all of the overlapping subcarriers 290 defined to be used for CRS REs 292 may instead be kept in the first subset 282. This may be beneficial in some of those implementations to improve the CRS signal quality required, reduce the level of distortion and/or improve the probability of successful CRS detection by an LTE receiver (for example to reduce the degradation of performance of channel estimation, enable proper RRM measurements, time/frequency tracking, etc.).
- LTE subcarriers 290 defined to be use for CRS REs 292 are included in the second subset 284, instead of mapping the CRS signal only to LTE subcarriers in the first subset 282, the CRS signal is also mapped to some or all of the LTE subcarriers in the second subset 284 (e.g. those that are normally used or defined for CRS REs) but at a reduced power level (lower than a power level used for mapping the CRS signal to subcarriers in the first subset 282). In some of those implementations, this may be beneficial to reduce the impairment to the detection of the Wi-Fi transmission at a W-Fi receiver.
- the W-Fi signal is also mapped to LTE subcarriers in the first subset 282 (e.g. those that overlap with a W-Fi subcarrier) but at a reduced power level (lower than a power level used for mapping the W-Fi signal to the subcarriers in the second subset 284).
- LTE subcarriers in the first subset 282 e.g. those that overlap with a W-Fi subcarrier
- a reduced power level lower than a power level used for mapping the W-Fi signal to the subcarriers in the second subset 284
- this may be beneficial to reduce the impairment to the detection of the CRS signal at an LTE receiver.
- the LTE system bandwidth is at least equal or greater than the W-Fi system bandwidth (e.g. 20 MHz).
- the second subset 284 may only include LTE subcarriers that correspond to the lower frequency components of the W-Fi transmission (i.e. the higher frequency components of the W-Fi transmission are truncated and not transmitted). For example, if the LTE system bandwidth is 10 MHz, the second subset 284 only includes LTE subcarriers that correspond to the W-Fi frequency components below 10 MHz (thereby truncating the frequency components above 10 MHz up to 20 MHz).
- the LTE system bandwidth is 10 MHz
- the second subset 284 only includes LTE subcarriers that correspond to the W-Fi frequency components below 10 MHz (thereby truncating the frequency components above 10 MHz up to 20 MHz).
- the second subset 284 may only include LTE subcarriers that correspond to the higher frequency components of the Wi-Fi transmission (i.e. the lower frequency components of the W-Fi transmission are truncated and not transmitted). Other possibilities exist for the second subset 284.
- an OFDM 1 transmitter may, in other implementations, use OFDM 1 subcarriers which are located in unused portions of the OFDM2 system bandwidth (and hence orthogonal to subcarriers in the used portion) to transmit additional OFDM 1 information.
- OFDM 1 subcarriers typically span the entire W-Fi system bandwidth (e.g.
- the W-Fi system bandwidth is limited by the IEEE 802.1 1 specified transmit spectral mask, defined as fc ⁇ 9 MHz (or 18 MHz wide) for a 20 MHz wide channel. For a 40 MHz wide channel, the IEEE 802.1 1 standard defines the transmit spectral mask as fc ⁇ 19 MHz (or 38 MHz wide).
- Transmit spectral masks are also defined for 80 and 160 M Hz wide channels.
- the subcarriers in the band edges are not employed to allow for sufficient attenuation of the transmitted signals' out-of-band emissions, for example, to accommodate filters in OFDM receivers designed without a sharp roll-off.
- non-Wi-Fi OFDM transmitters e.g. an LTE transmitter
- Figure 8 shows an example frequency diagram of a 20 MHz 802.1 1 a W-Fi channel system bandwidth that includes unused portions 294A, 294C at the lower and upper edges as well as in a middle portion 294B where the single 312.5 kHz W-Fi DC null subcarrier is normally set to zero.
- the amount of free, unused bandwidth at each of the lower and upper edges is 1 .71875 MHz, which represents half of (20 MHz - 53 x 312.5 kHz).
- 802.1 1 n/ac supports an additional 1.09375 MHz of unallocated or unused spectrum at the edge of each channel band.
- the size and location of unused spectral portions may be different depending on the type of OFDM2 communication protocol and the size of the channel (e.g. 20, 40, 80, 160 M Hz), the size and location of unused spectral portions may be different.
- an LTE transmitter operating in the same or an overlapping system bandwidth can therefore generate and/or transmit LTE signals using only those LTE subcarriers which are located in any one of the spectral portions 294A C not utilized or occupied by W-Fi subcarriers but located within the LTE system bandwidth.
- This approach applies irrespective of whether the LTE transmitter uses the entire W-Fi system bandwidth.
- a smaller LTE spectrum e.g. 18 MHz
- the 15 kHz LTE subcarrier spacing is substantially smaller than the 312.5 kHz Wi-Fi subcarrier spacing, a good number of LTE subcarriers orthogonal to the W-Fi subcarriers can be used.
- a narrower LTE subcarrier spacing (for example, of 3.75 kHz) may be employed for 3GPP Narrowband Internet of Things (loT) implementations, and future 3GPP 5G New Radio (NR) technology specifications may also include other subcarrier spacings such as 30 or 60 kHz, all of which are considerably less than the 312.5 kHz being employed in W-Fi.
- an LTE transmitter operating in the same or an overlapping system bandwidth can advantageously generate and transmit additional LTE data independently of whether the W-Fi channel is available or not. Also, as will be explained below in greater detail, if the W-Fi channel is busy, the LTE transmitter can limit its LTE transmissions to only use the LTE subcarriers in non-utilized portion(s) of the W-Fi system bandwidth. Alternatively, or additionally, if the W-Fi channel is idle, the LTE transmitter can be configured to operate as described above i.e.
- LTE and W-Fi signals concurrently (by partitioning the LTE available subcarriers into first and second subsets 282, 284) or in sequence (e.g. by using the LTE subcarriers to generate and/or transmit a W-Fi signal to reserve the channel for a subsequent LTE transmission).
- the number of LTE and W-Fi subcarriers used can be such that the LTE and/or W-Fi transmissions can be performed over either the entire LTE system bandwidth or limited to the W-Fi system bandwidth.
- the data can include one or more fields of the W-Fi transmission so that LTE receivers can be made aware of the concurrent W-Fi transmission and/or of an upcoming LTE transmission.
- the additional LTE data could include the source and destination MAC addresses and duration field of the CTS packet.
- the additional LTE data can be predetermined and include one or more information fields or elements of a Wi-Fi header or CTS packet to be sent concurrently over (used portions of) the W-Fi system bandwidth as described above.
- the additional data may include additional information specific to the LTE transmitter, such as a cell identification (I D), a location, or one or more connected network(s).
- I D cell identification
- Figure 9A shows a frequency diagram example where 1 14 LTE
- FIG. 9A only shows the LTE subcarriers in upper edge portion 294c but although not shown, it is understood that a similar number of additional LTE subcarriers could be located in the lower edge portion 294A as well as up to 20 additional LTE subcarriers could be used in the middle portion 294B (normally the W-Fi DC Null W-Fi subcarrier spacing).
- the LTE subcarriers in the non-utilized portions 294A C are included in the first subset 282 and the LTE subcarriers located within the portion of the W-Fi band normally occupied by W-Fi subcarriers (i.e. a utilized portion)) are included in the second subset 284 and used to generate and/or transmit W-Fi signals as described above in relation to Figures 7A-B.
- W-Fi circuitry e.g. a W-Fi module or transceiver
- some of the subcarriers used in the second subset 284 may instead be replaced with LTE subcarriers and allocated to the first subset 282 (in addition to LTE subcarriers located in the unused portions 294A C of the W-Fi band, leaving even more bandwidth to additional LTE data.
- FEC Forward Error Correction
- Figure 9B shows another frequency diagram example where the power level or amplitude of the LTE subcarriers in the upper edge portion 294c has been adjusted to meet a 20 MHz power spectral density mask 295 that might be imposed on transmissions within and around the Wi-Fi system bandwidth.
- the upper edge of the transmit mask 295 is flat up to +9 MHz from the channel center, then drops 20 dBr over the next 2 MHz to +1 1 MHz from the channel center.
- W-Fi receivers can handle high levels of (first) Adjacent Channel Interference (ACI) from channels which are ⁇ 20 MHz from the active 20 MHz W-Fi channel, and higher levels of (second) ACI from channels which are ⁇ 40 MHz from the active 20 M Hz W-Fi channel.
- ACI channels are sufficiently far enough away from the active 20 MHz channel, that filtering techniques can be applied to mitigate the high power interference signals which are not following the OFDM subcarrier spacing in the 20 M Hz W-Fi channel.
- Figures 9C and 9D show other frequency diagram examples where the power level of all of the LTE subcarriers in the upper edge portion 294c and the middle portion 294B has been lowered relative to a power level of the W-Fi subcarriers so that the energy from the additional LTE subcarriers does not significantly affect the W-Fi OFDM receiver.
- W-Fi receivers require a Signal-to- Interference-plus-Noise-Ratio (SIN R) of 5 dB (e.g.
- the total relative power of the injected LTE subcarriers should be lower than the desired W-Fi SI NR by 10 dB so as not to affect the W-Fi receive sensitivity by more than 0.1 dB.
- the additional LTE subcarriers represent less than 10% of the W-Fi channel bandwidth (or less than 2 MHz) and as such, their total relative power is already lower by 10 dB.
- the total relative power of the additional LTE subcarriers is reduced by the desired W-Fi SINR.
- the power level of the LTE subcarriers is reduced by 5 dB while the power level for high modulation rate (e.g. 64 QAM) MIMO transmissions, may require a further reduction (e.g. 30 dB).
- the LTE subcarriers are transmitted at the same or even higher power than the Wi- Fi carriers.
- the LTE transmitter configuration may include two separate and independent physical layers (LTE and W-Fi), with different ASIC components and/or circuitry that reflect differences in for example, the symbol durations, cyclic prefix durations, number of subcarriers, subcarrier spacing, subcarrier modulation formats, subcarrier frequencies, or any one of numerous MAC layer differences, but it does not preclude that a common ASIC or other hardware circuitry can be configured to support both OFDM technologies.
- LTE and W-Fi physical layers
- ASIC components and/or circuitry that reflect differences in for example, the symbol durations, cyclic prefix durations, number of subcarriers, subcarrier spacing, subcarrier modulation formats, subcarrier frequencies, or any one of numerous MAC layer differences, but it does not preclude that a common ASIC or other hardware circuitry can be configured to support both OFDM technologies.
- FIGS. 10A and 10B there is shown two different block diagram examples of an OFDM transmitter 300, 350 of a first (or base)
- OFDM1 e.g. a 3GPP or LTE technology
- OFDM2 subcarrier or symbol information of another OFDM technology
- the OFDM 1 transmitters 300, 350 operate in a similar fashion but as will be explained below in greater detail, implementations of the OFDM 1 transmitter 300 use time-domain interpolation to generate the OFDM2 information (e.g. using a Time-Domain (TD) Interpolator 314) while implementations of the OFDM 1 transmitter 350 use frequency-domain interpolation instead (e.g. using a Frequency-Domain
- TD Time-Domain
- the OFDM 1 transmitter 300, 350 is configured to generate OFDM 1 signals carrying OFDM 1 or OFDM2 information and to transmit the signals generated concurrently or in sequence.
- the first and second OFDM 1 signals are transmitted concurrently over an OFDM2 system bandwidth (e.g. a Wi-Fi system bandwidth), where, for example, the second OFDM 1 signal is transmitted over portion(s) of the OFDM2 system bandwidth normally used or occupied by OFDM2 subcarriers while the first OFDM 1 signal is transmitted over non-utilized portion(s) of the OFDM2 system bandwidth.
- the first OFDM 1 signal may be generated by mapping a first predetermined OFDM 1 signal to a first subset of the available OFDM 1 subcarriers (e.g. OFDM 1 subcarriers located in unused portions of the OFDM2 system bandwidth) while the second OFDM 1 signal may be generated by mapping a second predetermined OFDM2 signal (e.g. a CTS-to-Self packet or W-Fi header) to a second subset of the OFDM 1 subcarriers (e.g. OFDM 1 subcarriers located in the used portions of the OFDM2 system bandwidth).
- a first predetermined OFDM 1 signal to a first subset of the available OFDM 1 subcarriers (e.g. OFDM 1 subcarriers located in unused portions of the OFDM2 system bandwidth)
- a second predetermined OFDM2 signal e.g. a CTS-to-Self packet or W-Fi header
- the first OFDM 1 signal may include parameters or data indicative of the concurrent OFDM2 transmission so that OFDM 1 receivers can be made aware of the concurrent OFDM2 transmission and/or any subsequent OFDM 1 transmissions.
- the OFDM 1 transmitter 300, 350 may be additionally configured to transmit a subsequent (e.g. a third) OFDM 1 signal using the M OFDM 1 subcarriers.
- the OFDM2 information transmitted and subsequent OFDM 1 signal transmission may be contiguous or non-contiguous.
- the OFDM 1 transmitter 300, 350 may use the OFDM2 transmission to encode various types of OFDM2 related information for various purposes, including for example to reserve a channel for a certain duration, to indicate a transmission time associated with the OFDM2 and/or the subsequent OFDM 1 signal transmission or to create a carrier sense indication, for example, to cause OFDM2 receivers to consider the channel as busy.
- the OFDM2 transmission includes Wi-Fi header data and/or W-Fi packet data and the subsequent OFDM 1 signal transmission includes LTE data (or LTE TTIs) and the W-Fi header or packet data in the OFDM2 transmission is indicative of a transmission length, a transmission time, a transmission type and/or a channel reservation time associated with the W-Fi header/packet data, the LTE data or a combination of both.
- the OFDM 1 transmitter 300 has an OFDM 1 transmission chain 302, an OFDM 1 subcarrier mapping unit 308, an OFDM1 Inverse Fast Fourier Transform (I FFT) unit 304 and an OFDM 1 RF unit 306 (e.g. DAC, mixer, and PA) which, in combination, are configured to generate and transmit a first OFDM 1 signal 320 via one or more antennas 307.
- the OFDM 1 transmission chain 302 generates (i.e converts) a serial OFDM 1 symbol stream of Binary Phase Shift Keying (BPSK) or Quadrature Amplitude Modulation (QAM) data into M parallel streams.
- BPSK Binary Phase Shift Keying
- QAM Quadrature Amplitude Modulation
- a predetermined OFDM 1 signal is modulated onto (some or all of) the M base OFDM 1 subcarriers via the OFDM 1 subcarrier mapping unit 308 to produce the first OFDM 1 signal 320 which, after conversion into the time domain in the I FFT unit 304, is transmitted via the RF unit 306 and antenna 307.
- the OFDM 1 transmitter 300 also includes circuitry that is configured to produce a second OFDM 1 signal 322 to carry OFDM2 information for transmission via the antenna 307.
- the circuitry includes an OFDM2 signal generator 312 configured to generate an OFDM2 signal.
- the OFDM2 signal is a time-domain signal that contains predetermined or defined OFDM2 symbol information generated with, for example, N OFDM2 subcarriers.
- the circuitry further includes an OFDM2-OFDM 1 Time-Domain (TD) interpolator 314 that interpolates in the time-domain the OFDM2 signal generated (further details below).
- TD Time-Domain
- the circuitry includes an OFDM 1 signal memory 316 where the FDS signal is stored.
- the OFDM 1 transmitter 300 determines that OFDM2 information needs to be transmitted, it generates the FDS dynamically (e.g. on the fly) using the signal generator 312 and TD interpolator 314 or simply reads the FDS signal from the signal memory 316 and routes it to the OFDM 1 subcarrier unit 308.
- the OFDM 1 subcarrier mapping unit 308 maps the FDS signal to (some or all of) the M
- the circuitry may only include signal memory 316.
- the stored FDS signal is a predetermined or defined vector of OFDM 1 (frequency- domain) subcarrier modulation values (e.g. a vector with M values) that includes values representative of predetermined or defined OFDM2 information.
- STF_LTE_SCs [-499, -415, -332, -249, -165, -82, 85, 168, 252, 335, 418, 502]
- STF_LTE_SC_Value V(13/6)*[1 +i, -1 -i, 1 +i, -1 -i, -1 -i, 1 +i, -1-i, -1 -i, 1 +i, 1 +i, 1 +i, 1 +i] [00112]
- the twelve LTE subcarriers identified above are those that overlap with at least one Wi-Fi subcarrier (or a main lobe thereof) i.e. the W-Fi subcarrier(s) normally used to produce an STF.
- all other LTE subcarriers are set to a zero value (e.g. (0+Oi)).
- LTF_LTE_SCs [-540, -519, 499, -478, -457, -436, -415, -394, -374, -353,
- LTF_LTE_SC_Value [1 , 1, -1, -1, 1, 1, -1, 1, -1, 1, 1, 1, 1, 1, 1, 1, 1, -1, -1, 1, 1, -
- LTF_LTE_SCs array by sequence number is set to a corresponding non-zero modulation value in the LTF_LTE_SC_Value array.
- the fifty-two LTE subcarriers identified above in this example are those that overlap with at least one W-Fi subcarrier (or a main lobe thereof) i.e. the W-Fi subcarrier(s) normally are used to produce an LTF.
- all other LTE subcarriers are set to a zero value (e.g. (0+Oi).
- the OFDM 1 transmitter 300 may be configured to transmit the first and second OFDM 1 signals 320, 322 either at the same or at different times.
- the OFDM 1 mapping unit 308 is configured to map the OFDM 1 transmission chain output (e.g. the predetermined OFDM 1 signal) to all of the M OFDM 1 subcarriers.
- the OFDM 1 mapping unit 308 is configured to map the FDS signal to all of the M OFDM 1 subcarriers.
- a switch or other switching means may be used to route either the OFDM 1 transmission chain output or the FDS signal into the OFDM 1 subcarrier mapping unit 308 to selectively produce either the first or second OFDM 1 signal 320, 322 so that they can be converted into the time domain in IFFT unit 304 (as time-domain signal 324) and transmitted via the RF unit 306 and antenna 307
- the OFDM 1 transmitter 300 may include circuitry configured to generate the second OFDM 1 signal as a time-domain signal.
- the circuitry may include the OFDM2 signal generator 312 and TD interpolator 314 configured to produce the second OFDM 1 signal as a time-domain OFDM 1 signal 326, TDS, to carry the OFDM2 information.
- the OFDM 1 transmitter 300 when it determines that the OFDM2 information needs to be transmitted, the OFDM 1 transmitter 300 generates and routes the TDS signal 326 into the OFDM 1 RF unit 306 via a switch (not shown) directly from the TD interpolator 314 or via the signal memory 316.
- the circuitry may only include signal memory 316.
- the stored TDS signal 326 is a predetermined or defined vector of OFDM 1 (time-domain) samples (e.g. a vector with M samples) that is representative of predetermined or defined OFDM2 information.
- the switch is part of a switching module (not shown) that is configured to determine when OFDM2 information needs to be transmitted and based on that determination, to route the FDS (or TDS) signal containing the OFDM2 information (e.g. the second predetermined OFDM2 signal) to the OFMD1 subcarrier mapping unit 308 (or OFDM 1 RF 306) or route the
- OFDM 1 transmission chain output (e.g. the first predetermined OFDM 1 signal) for transmission via the RF unit 306.
- the switching module controls whether OFDM2 or OFDM 1 information is transmitted via the OFDM 1 subcarrier mapping unit 308 and/or via RF unit 306. For example, when the switching module determines that OFDM2 information needs to be transmitted (e.g. when a Wi-Fi preamble or CTS packet needs to be sent to reserve the channel for a subsequent LTE
- the switching module routes the FDS signal (or TDS signal) containing the OFDM2 information (e.g. the second predetermined OFDM2 signal) to the OFDM 1 subcarrier mapping unit 308 (or OFDM 1 RF 306) for transmission as a set of OFDM2 symbols.
- the switching module determines that OFDM 1 information needs to be transmitted (e.g. the subsequent LTE transmission)
- the switching module instead routes the output of the OFDM 1 transmission chain 302 containing the OFDM 1 information (e.g. the first predetermined OFDM 1 signal) to the OFDM 1 subcarrier mapping module 308 for transmission via the OFDM 1 RF 306 as a set of OFDM 1 symbols.
- the OFDM 1 mapping unit 308 is instead configured to map the OFDM 1 transmission chain output to a first subset 282 of the M OFDM 1 subcarriers to produce the first OFDM 1 signal 320 and the FDS to the second subset 284 to produce the second OFDM 1 signal 322.
- the first and second OFDM1 signals 320, 322 are then coupled to the IFFT unit 304 to produce time-domain signal 324 carrying both the OFDM 1 and OFDM2 information and which can be transmitted via the RF unit 306 and antenna 307.
- the subcarrier mapping functionality described above could alternatively be implemented in a different location within the OFDM 1 transmitter 300.
- the functionality for mapping the FDS signal to the second subset 828 could be located within the TD interpolator 314. Other possibilities exist.
- the OFDM 1 transmitter 300 may optionally include a combiner unit 310 to combine the first and second OFDM 1 signals 320, 326 in the time domain.
- the TD interpolator 314 generates the second OFDM 1 signal as TDS signal 326 using the second subset 284 of subcarriers so that it can be combined in combiner 310 with the first OFDM 1 signal 320 (assuming it was generated with the first subset 282 in the OFDM 1 subcarrier mapping unit 308) for concurrent transmission via the RF unit 306 and antenna 307.
- a channel availability check is performed first (e.g. by a receiver in communication with the OFDM 1 transmitter 300) to determine whether the transmission channel or band used is free. This check may be based on whether a carrier wave, signal or energy can be detected in the channel or band of interest (e.g. with a -62 dBm threshold). If no carrier or energy is detected, the OFDM 1 transmitter 300 transmits the first and second OFDM 1 signals 320, 322 (or 326) concurrently or in sequence.
- the switching module may rely on a channel availability indication provided by a channel availability unit (not shown) before it can determine that OFDM 1 and/or OFDM2 information can be transmitted.
- a channel availability unit not shown
- the OFDM 1 transceiver 300 may be configured to transmit a time-domain signal that can be fed directly into the
- the switching module may be configured, when it receives a positive channel availability indication, to route a repeatable time domain signal directly into the RF unit 306 until the desired OFDM2 information is ready for transmission.
- the repeatable time-domain signal is another OFDM 1 signal containing OFDM2 information which has a repetitive or cyclical pattern.
- the repeatable OFDM2 information is a sequence of LTFs and/or STFs. Other possibilities exist for the repeatable time-domain signal used prior to transmitting the desired OFDM2 information.
- FIG. 1 1 shows a block diagram example of a configuration for the OFDM2 signal generator 312 and OFDM2-OFDM 1 TD interpolator 314 of Figure 10A to generate and interpolate a Wi-Fi signal into an LTE signal in the time domain, in accordance to principles described herein.
- a W-Fi signal generator 402 includes a 64-point W-Fi IFFT unit 406 that is configured to perform an IFFT for each symbol time duration of a frequency-domain W-Fi signal 404 carrying pre-determined or defined W-Fi information (e.g. a W-Fi header or packet).
- the W-Fi signal generator 402 also includes a CP unit 408 that is configured to add a CP to each W-Fi symbol generated to create a set of W-Fi symbols carrying the pre-determined W-Fi information.
- the W-Fi symbol set is fed into a LTE time-domain interpolator 412 that includes a re-sampling unit 414 configured to resample (e.g. by time-domain interpolation or low pass filtering) the W-Fi symbol set to produce a time-domain LTE signal 420 (e.g. C-PRI l/Q data).
- the LTE time-domain interpolator 412 may, in some implementations, include a padding unit 416 to pad the LTE signal 420 to turn it into an LTE l/Q vector (e.g. the TDS signal of Figure 10A) that can be processed by conventional LTE RF circuitry (e.g. the OFDM 1 RF unit 306 of Figure 10A).
- the LTE time-domain interpolator 412 may further include an LTE FFT unit 418 to obtain a corresponding LTE signal 422 in the frequency-domain (e.g. the FDS signal of Figure 10A) that can be processed by conventional LTE I FFT circuitry (e.g. the OFDM 1 IFFT unit 304 of Figure 10A).
- the LTE FFT unit 418 has an input size equal to the total size of the Wi-Fi symbols in the Wi-Fi symbol set and an output equal to the number of LTE subcarriers (e.g. 2048).
- the LTE FFT unit 418 used is the same as that used in a conventional LTE receiving chain.
- Other LTE FFT unit 418 is the same as that used in a conventional LTE receiving chain.
- the OFDM 1 transmitter 350 is configured to generate and transmit first and second OFDM 1 signals 370 and 372 (or 376) and includes an OFDM 1 transmission chain 352, an OFDM 1 subcarrier mapping unit 358, an IFFT unit 354, an optional combiner unit 360, an OFDM 1 RF unit 356, antenna(s) 357, and circuitry including an OFDM2 signal generator 362, OFDM2- OFDM 1 interpolator 364 and/or an OFDM 1 signal memory 366.
- the OFDM 1 transmitter 350 may also optionally include a switch or switching module (not shown) that is configured as described above in relation to Figure 10A e.g. to determine when OFDM2 information needs to be transmitted (with or without a prior channel availability check). Based on that determination, the switching module is also configured to route the FDS (or TDS) signal containing the OFDM2 information (e.g. the second predetermined OFDM2 signal) to the OFMD1 subcarrier mapping unit 358 (or OFDM 1 RF 306) or route the OFDM 1 transmission chain output (e.g. the first predetermined OFDM 1 signal) for transmission via the RF unit 356.
- a switch or switching module (not shown) that is configured as described above in relation to Figure 10A e.g. to determine when OFDM2 information needs to be transmitted (with or without a prior channel availability check). Based on that determination, the switching module is also configured to route the FDS (or TDS) signal containing the OFDM2 information (e.g. the second predetermined OFDM2 signal) to the OF
- the OFDM 1 transmitter 300 may also optionally include a combiner unit 360 to combine the first and second OFDM 1 signals 320, 326 in the time domain prior to transmission.
- the FD interpolator 364 generates the second OFDM 1 signal 376 as a time-domain signal TDS using the second subset 284 of subcarriers so that it can be combined in combiner 360 with the first OFDM 1 signal 320 for concurrent transmission via the RF unit 306 and antenna 307
- FIG. 12 shows a block diagram example of a configuration for the OFDM2-OFDM1 FD interpolator 364 of Figure 10B denoted as FD interpolation 452 which is configured to interpolate, in the frequency domain, a Wi-Fi signal 456 carrying pre-determined or defined W-Fi information (e.g. a W-Fi header or packet) into an LTE signal 470, 472.
- the FD interpolation unit 452 includes a symbol interpolator 458 that interpolates on a W-Fi symbol-by-symbol basis i.e. one W-Fi symbol at a time.
- the symbol interpolator 458 that interpolates on a W-Fi symbol-by-symbol basis i.e. one W-Fi symbol at a time.
- the symbol interpolator 458 that interpolates on a W-Fi symbol-by-symbol basis i.e. one W-Fi symbol at a time.
- the symbol interpolator 458 that interpolates on
- interpolator 458 interpolates the N (e.g. 64) W-Fi subcarriers into M (e.g. 2048) LTE subcarriers using the following "sine" function:
- symbol interpolator 458 may be used to map N W-Fi subcarriers into M LTE subcarriers.
- the symbol interpolator 458 takes as input the W-Fi signal 456 in the frequency domain that corresponds to one W-Fi symbol time duration.
- the output is fed into an LTE IFFT unit 460 which produces a set of M time-domain samples (e.g. 2048) which span over one LTE symbol duration.
- the time-domain set of M samples is truncated in truncation unit 464 (e.g. by selecting a subset of samples (e.g. 98)) to correspond to one W-Fi symbol duration (e.g. 3.2 ⁇ ) thereby producing LTE l/Q data corresponding to the one W-Fi symbol duration processed by the symbol interpolator 458.
- the FD interpolation unit 452 also includes a concatenation unit 464 that concatenates the LTE l/Q data produced with any LTE l/Q data that might have been produced for Wi-Fi symbols previously processed by the interpolator 452.
- the W-Fi symbols are thus processed in the FD interpolation unit 452 until all of the W-Fi symbols in the W-Fi signal have been processed.
- the concatenation unit 464 produces a time-domain LTE signal or l/Q vector 470 (e.g. the TDS signal of Figure 10B) formed of the concatenated LTE l/Q data corresponding to the entire W-Fi signal) so that it can then be processed by conventional LTE RF circuitry (e.g.
- the FD interpolating unit 452 may, in some implementations, include an LTE FFT unit 468 to obtain a corresponding LTE signal 472 in the frequency-domain (e.g. the FDS signal of Figure 10B) that can be processed by conventional LTE IFFT circuitry (e.g. the OFDM 1 I FFT unit 354 of Figure 10B).
- LTE FFT unit 468 is the same as that used in in a conventional LTE receiving chain. Other implementations are possible.
- Figure 13A shows an example method 600 for the OFDM transmitter 300 of Figure 10A.
- the OFDM transmitter 300 is assumed to be configured for OFDM signal transmissions using a first plurality of subcarriers Mi having a first subcarrier frequency spacing ⁇ defining a first symbol duration Ti .
- the method 600 includes mapping in the frequency domain a first predetermined OFDM signal to a first subset of a first plurality Mi of subcarriers to produce a first OFDM signal, the first plurality Mi of subcarriers having a first subcarrier frequency spacing ⁇ and a first symbol duration Ti .
- the method further includes interpolating in the time domain a second predetermined OFDM signal to produce an interpolated OFDM signal associated with the first plurality Mi of subcarriers, the second predetermined OFDM signal being associated with a second plurality of subcarriers N 2 having a second subcarrier frequency spacing ⁇ 2 > ⁇ and a second symbol duration T 2 ⁇ Ti .
- the method further includes mapping in the frequency domain the interpolated OFDM signal to a second subset of the first plurality Mi of subcarriers to produce a second OFDM signal, the second subset of subcarriers being different from the first subset.
- the method includes transmitting, during one or more first symbol durations Ti , the first OFDM signal using the first subset of subcarriers and the second OFDM signal using the second subset of subcarriers.
- the method 600 includes, prior to mapping the interpolated OFDM signal to the second subset, performing an Mi point FFT of the interpolated OFDM signal.
- the method 600 further includes performing an Mi point I FFT of the first and second OFDM signals for transmission during one or more first symbol durations Ti .
- the second predetermined OFDM signal includes a plurality of second OFDM symbols, each represented by N 2 points where N 2 is smaller than ML
- the interpolating of the second predetermined OFDM signal includes resampling the predetermined OFDM signal to obtain Mi points.
- the second predetermined OFDM signal is generated using an N 2 point IFFT.
- the second predetermined OFDM signal is read from a memory.
- Mi is a number of LTE subcarriers and N 2 is a number of Wi-Fi subcarriers.
- Other implementations are possible.
- FIG. 13B shows an example method 700 for the OFDM transmitter 350 of Figure 10B.
- the OFDM transmitter 350 is assumed to be configured for OFDM signal transmissions using a first plurality of subcarriers Mi having a first subcarrier frequency spacing ⁇ defining a first symbol duration Ti .
- the method 700 includes a set of steps 702, 704, 706, 708 which are performed for each one of a plurality of OFDM symbols of a second predetermined OFDM signal, the OFDM symbols being associated with a second plurality of subcarriers N 2 having a second subcarrier frequency spacing ⁇ 2 > ⁇ and a second symbol duration T 2 ⁇ Ti .
- the method 700 includes at step 702, mapping in the frequency domain a first predetermined OFDM signal to a first subset of a first plurality Mi of subcarriers to produce a first OFDM signal, the first plurality Mi of subcarriers having a first subcarrier frequency spacing ⁇ and a first symbol duration Ti .
- the method includes interpolating in the frequency domain one OFDM symbol of a second predetermined OFDM signal to produce an interpolated OFDM symbol associated with the first plurality Mi of subcarriers, the second predetermined OFDM signal being associated with a second plurality of subcarriers N 2 having a second subcarrier frequency spacing ⁇ 2 > ⁇ and a second symbol duration T 2 ⁇ Ti .
- the method further includes at step 706
- the method includes concatenating in the time domain the truncated OFDM symbol with any previously concatenated OFDM symbol(s) of the predetermined OFDM signal.
- step 710 steps 702-708 were performed for the last of the plurality of OFDM symbols
- the method 700 goes to step 712 where it includes mapping in the frequency domain the concatenated OFDM symbol(s) to a second subset of subcarriers from the first plurality Mi of subcarriers, different from the first subset, to produce a second OFDM signal and at step 714, transmitting, during one or more first symbol durations Ti , the first OFDM signal using the first subset of subcarriers and the second OFDM signal using the second subset of subcarriers. Otherwise, the method 700 goes back and performs steps 702-708 for the next OFDM symbol until all of the OFDM symbols have been processed.
- the method further includes prior to mapping in the frequency domain the concatenated OFDM symbol(s), performing an Mi point FFT of the concatenated OFDM symbol(s).
- the method 700 further includes performing an Mi point IFFT of the first and second OFDM signals for transmission during one or more first symbol durations Ti .
- the symbol interpolating is performed in accordance with the following function:
- Mi is a number of LTE subcarriers and N 2 is a number of Wi-Fi subcarriers.
- OFDM2 symbol information (e.g. Wi-Fi symbol information) generated as an OFDM 1 signal based on the principles described above can be received and demodulated by an OFDM2 receiver (e.g. W-Fi) despite the fact that they have been generated by an OFDM 1 transmitter (e.g. LTE) with OFDM 1 subcarriers, with or without a concurrent OFDM 1 transmission.
- an OFDM2 receiver is configured to receive, using N OFDM2 subcarriers, OFDM2 symbol information generated with M (or less than M) OFDM 1 subcarriers.
- the OFDM2 receiver includes an N-point FFT to receive the OFDM2 symbol information which was generated with an M-point I FFT in the OFDM 1 transmitter.
- the OFDM2 receivers is configured to receive, using N OFDM2 subcarriers, OFDM2 symbol information generated with M (or less than M) OFDM 1 subcarriers that overlap with at least one of the N subcarriers (or a main lobe thereof). Other possibilities exist for the OFDM2 receiver.
- the OFDM2 symbol information includes predetermined OFDM2 control or packet data which is indicative of one of a transmission length, transmission time, transmission type and a channel reservation time associated with the OFDM2 symbol set, an OFDM 1 symbol set transmitted after the OFDM2 symbol set or a combination thereof.
- predetermined OFDM2 control or packet data which is indicative of one of a transmission length, transmission time, transmission type and a channel reservation time associated with the OFDM2 symbol set, an OFDM 1 symbol set transmitted after the OFDM2 symbol set or a combination thereof.
- Figure 14A shows a flow chart of another example method 800 for the OFDM transmitters 300, 350 of Figures 10A-B in accordance with the principles described herein.
- the method 800 includes generating a first OFDM signal containing data associated with a first OFDM communication protocol where the first OFDM communication protocol is defined to use a first system bandwidth that overlaps with a second system bandwidth associated with a second OFDM communication protocol.
- the method further includes transmitting the first OFDM signal over a non-utilized portion of second system bandwidth.
- FIG 14B shows a flow chart of yet another example method 900 for the OFDM transmitters 300, 350 of Figures 10A-B in accordance with the principles described herein.
- the method 900 includes generating a first OFDM signal containing data associated with a first OFDM communication protocol.
- the first OFDM communication protocol is defined to use a first system bandwidth that overlaps with a second system bandwidth associated with a second OFDM communication protocol. If a determination is made at step 904 that another transmission is in progress in the second system bandwidth (e.g. channel is busy), the method proceeds to step 906 and includes transmitting the first OFDM signal over a non-utilized portion of second system bandwidth. If, on the other hand, a determination is made that no other transmission is in progress (e.g.
- the method includes generating at step 908 a second OFDM signal containing data associated with the second OFDM communication protocol and transmitting at step 910 the second OFDM signal over the second system bandwidth where the second OFDM signal is indicative of one of a transmission length, transmission time, transmission type and a channel reservation time associated with at least one of the first and second OFDM signals. Finally, the method includes at step 912 transmitting the second OFDM signal over the second system bandwidth.
- the first OFDM signal is transmitted using a first subset of a first plurality of subcarriers having a first subcarrier frequency spacing where the first subset is located in the non-utilized portion of the second system bandwidth.
- the second OFDM signal is transmitted using either a second plurality of subcarriers having a second subcarrier frequency spacing different than the first subcarrier frequency spacing or using a second subset of subcarriers from the first plurality of subcarriers, different from the first subset.
- the second subset or the second plurality of subcarriers is located in a utilized portion of the second system bandwidth.
- the first OFDM signal is transmitted at a power level different than a power level for the second OFDM signal.
- the first OFDM signal is an LTE signal and the second OFDM signal includes one of a CTS frame, an STF, an LTF and a SIG.
- FIGS 15A-B are block diagrams of exemplary embodiments of respectively a (first) OFDM 1 transmitting node 1000 (e.g. an LTE transmitter) and an OFDM2 receiving node (e.g. a Wi-Fi receiver) configured respectively to transmit and receive OFDM 1 signals in accordance with the principles of the present disclosure.
- a (first) OFDM 1 transmitting node 1000 e.g. an LTE transmitter
- an OFDM2 receiving node e.g. a Wi-Fi receiver
- OFDM 1 transmitting node 1000 (e.g. configured for OFDM 1 signal transmissions) includes a transceiver 1002, one or more processor(s) 1004, memory 1006 which includes one or more of a generation module 1008, an interpolation module 1010, a signal memory module 1012, a switching module (not shown), a subcarrier mapping module 1014 and a transmitting module 1016.
- the transceiver 1002 may be replaced by a transmitter and a receiver (not shown).
- the generation module 1008 is configured to perform the signal generation functionality described above which includes generating a first predetermined OFDM 1 signal containing OFDM 1 information (e.g.
- the interpolation module 1010 is configured to perform the interpolation functionality described above, which includes interpolating the predetermined OFDM2 signal generated to produce a second predetermined OFDM 1 signal that contains the predetermined or defined OFDM2 information.
- the signal memory module 1012 is configured to perform the storing functionality described above which includes storing the second predetermined OFDM 1 signal that contains the OFDM2 information.
- the switching module (not shown) is configured to perform the switching functionality described above, which includes controlling whether and when OFDM2 or OFDM 1 information is transmitted via the transmitting module 1016.
- the subcarrier mapping module 1014 is configured to perform the mapping functionality described above, which includes mapping the first predetermined OFDM 1 signal containing the OFDM 1 information to all (or a first subset) of OFDM 1 subcarriers to produce a first OFDM 1 signal and mapping the second predetermined OFDM 1 signal containing the OFDM2 information to all (or a second subset) to produce a second OFDM 1 signal.
- the transmitting module 1016 is configured to perform the transmitting functions described above which includes transmitting the first OFDM 1 signal over a non-utilized portion of second system bandwidth signals and transmitting the second OFDM 1 signal over (a used portion of) the second system bandwidth.
- the memory 1006 may only include the generation module 1008 and the transmitting module 1016 respectively performing the functions described above.
- the OFDM2 information is stored in the signal memory module 1012 in advance, and the memory 1006 only includes the signal memory module 1012, the subcarrier mapping module 1014 and the transmitting module 1016 respectively performing the functions described above.
- the generation module 1008, interpolation module 1010, signal memory module 1012, switching module, subcarrier mapping module 1014, and transmitting module 1016 are implemented at least partially in the memory 1006 in the form of software or (computer-implemented) instructions executed by the processor(s) 1004 within the OFDM 1 transmitting node 1000 or distributed across two or more nodes (e.g. , the OFDM 1 transmitting node 1000 and another node).
- the processor(s) 1004 includes one or more hardware components (e.g., Application Specific Integrated Circuits (ASICs)) that provide some or all of the generation, interpolation, storing, switching, mapping and transmitting functionality described above.
- ASICs Application Specific Integrated Circuits
- the processor(s) 1004 include one or more hardware components (e.g., Central Processing Units (CPUs)), and some or all of the generation, interpolation, storing, switching, mapping and transmitting functionality described above is implemented in software stored in, e.g. , the memory 1006 and executed by the processor 1004.
- the processor(s) 1004 and memory 1006 form processing means (not shown) configured to perform the generation, interpolation, storing, switching, mapping and transmitting functionality described above.
- OFDM2 receiving node 1 100 includes a transceiver 1 102, one or more processor(s) 1 104, and memory 1 106 which includes a receiving module 1 108, and a transmission control module 1 1 10.
- the transceiver 1 102 may be replaced by a transmitter and a receiver (not shown).
- the receiving module 1 108 is configured to perform the receiving functionality described above which, as noted above includes receiving using OFDM2 subcarriers, an OFDM 1 signal containing OFDM2 information (e.g. a Wi-Fi header or CTS packet) transmitted from an OFDM 1 transmitting unit using OFDM 1 subcarriers.
- OFDM2 information e.g. a Wi-Fi header or CTS packet
- the transmission control module 1 1 10 which may be optional depending on the implementation, is configured to perform the transmission control functionality described above, which includes determining if the OFDM 1 signal contains data indicative of one of a transmission length, a transmission time, a transmission type, and/or a channel reservation time associated with at least one of the first and second OFDM signals and if so, refraining from transmitting based on the data received.
- the receiving module 1 108 and transmission control module 1 1 10 are implemented at least partially in the memory 1 106 in the form of software or (computer-implemented) instructions executed by the processor(s) 1 104 within the OFDM2 receiving node 1 100 or distributed across two or more nodes (e.g. , the OFDM2 receiving node 1 100 and another node or device).
- the processor(s) 1 104 includes one or more hardware components (e.g. ,
- the processor(s) 1 104 include one or more hardware components (e.g. , Central Processing Units (CPUs)), and some or all of the receiving and transmission control functionality described above is implemented in software stored in, e.g., the memory 1 106 and executed by the processor 1 104.
- the processor(s) 1 104 and memory 1 106 form processing means (not shown) configured to perform the receiving and transmissions control functionality described above.
- an OFDM 1 receiving node may be structured in a manner similar to the OFDM2 receiving node 1 100 to receive and process an OFDM 1 signal transmitted using non-utilized portion(s) of an OFDM2 system bandwidth. As such, it may include a transceiver (or separate
- the transmitter/receiver includes one or more processor(s), and a memory which includes at least a receiving module.
- the receiving module is configured to receive, using OFDM 1 subcarriers, an OFDM 1 signal transmitted using non-utilized portion(s) of an OFDM2 system bandwidth.
- the OFDM 1 signal may be predetermined LTE data that includes one or more information fields or elements of a Wi-Fi header or CTS packet that has been sent concurrently to Wi-Fi receivers over (used portions of) the W-Fi system bandwidth for example, to reserve the channel for a subsequent LTE transmission.
- OFDM 1 receivers configured to receive an OFDM 1 signal transmitted over non-utilized portion(s) of an OFDM2 system bandwidth.
- Figures 16A-B show a variant for each of the OFDM transmitting and receiving node examples of Figures 15A-B, denoted respectively as OFDM transmitting node 1200, and ODFM receiving node 1300.
- 1200, 1300 includes a transceiver 1202, 1302 and circuitry containing (computer- implemented) instructions which when executed by one or more processor(s) 1 1204, 1304 cause their respective node 1200, 1300 to perform some or all of the generation, interpolation, storing, mapping, transmitting, receiving and
- the circuitry includes the respective memory 1206, 1306 and processor(s) 1204, 1304 which, similarly to the example nodes 1000 and 1 100 of Figures 15A-B may be implemented in many different ways.
- the memories 1206, 1306 contain instructions which, when executed, cause the respective node 1200, 1300 to perform some or all of their generation, interpolation, storing, mapping, transmitting, receiving and transmission control functionality described above.
- Other implementations are possible.
- Other embodiments are possible.
- a method for an OFDM transmitter or transmitting node configured for OFDM signal transmissions.
- the method includes generating a first OFDM signal containing data associated with a first OFDM communication protocol, where the first OFDM communication protocol is defined to use a first system bandwidth that overlaps with a second system bandwidth associated with a second OFDM communication protocol.
- the method further includes transmitting the first OFDM signal over a non-utilized portion of the second system bandwidth.
- the first OFDM signal is transmitted using a first subset of a first plurality of subcarriers having a first subcarrier frequency spacing, where the first subset is located in the non-utilized portion of the second system bandwidth.
- the method further includes generating a second OFDM signal containing data associated with the second OFDM communication protocol, and transmitting the second OFDM signal over the second system bandwidth.
- the first and second OFDM signals are transmitted at a same or a different time.
- transmitting the first OFDM signal includes transmitting the first OFDM signal over the non-utilized portion of the second system bandwidth if another transmission is in progress in the second system bandwidth.
- the method further includes, prior to transmitting the first OFDM signal, transmitting the second OFDM signal over the second system bandwidth, where the second OFDM signal is indicative of one of a transmission length, transmission time, transmission type and a channel reservation time associated with at least one of the first and second OFDM signals, and where the first OFDM signal is subsequently transmitted over the second system bandwidth.
- the second OFDM signal is transmitted using a second plurality of subcarriers having a second subcarrier frequency spacing different than the first subcarrier frequency spacing, where the second plurality of subcarriers is located in a utilized portion of the second system bandwidth.
- the second OFDM signal is transmitted using a second subset of subcarriers from the first plurality of subcarriers, different from the first subset, where the second subset being located in the utilized portion of the second system bandwidth.
- the first and second OFDM signals are generated in one of a time domain and a frequency domain, based on respective first and second predetermined OFDM signals containing data associated with the first and second OFDM communication protocols.
- generating the first OFDM signal includes mapping the first predetermined OFDM signal to subcarriers in at least the first subset and where generating the second OFDM signal includes mapping the second predetermined OFDM signal to subcarriers in at least the second subset.
- the second subset includes at least one subcarrier overlapping in frequency with a subcarrier of the second plurality of subcarriers.
- generating the second OFDM signal further includes generating the second predetermined OFDM signal, and interpolating the second predetermined OFDM signal generated using the first plurality of subcarriers to produce an interpolated OFDM signal that can be mapped to subcarriers in the second subset.
- the first OFDM communication protocol includes an LTE protocol and the second OFDM communication protocol includes an 802.1 1 protocol.
- the first OFDM signal includes an LTE signal and the second OFDM signal includes one of a Clear To Send (CTS) frame, a Short Training Field (STF), a Long Training Field (LTF), and a Signal Field (SIG).
- CTS Clear To Send
- STF Short Training Field
- LTF Long Training Field
- SIG Signal Field
- the first OFDM signal is transmitted at a power level different than a power level for the second OFDM signal.
- an OFDM transmitter or transmitting node configured for OFDM signal transmissions.
- the OFDM transmitter includes circuitry containing instructions which, when executed, are configured to cause the transmitter to perform any of the method embodiments described above.
- a non-transitory computer readable memory configured to store executable instructions for an OFDM transmitter or transmitting node configured for OFDM signal transmissions.
- the executable instructions when executed by a processor are configured to cause the OFDM transmitter to perform any of the method embodiments described above.
- an OFDM transmitter or transmitting node configured OFDM signal transmissions
- the OFDM transmitter includes a transceiver, a processor and a memory containing a generation module configured to generate a first OFDM signal containing data associated with a first OFDM communication protocol, where the first OFDM communication protocol is defined to use a first system bandwidth that overlaps with a second system bandwidth associated with a second OFDM communication protocol.
- the memory also contains a transmitting module configured to transmit the first OFDM signal over a non-utilized portion of the second system bandwidth.
- the first OFDM signal is transmitted using a first subset of a first plurality of subcarriers having a first subcarrier frequency spacing, where the first subset is located in the non-utilized portion of the second system bandwidth.
- the memory also contains a generation module configured to generate a second OFDM signal containing data associated with the second OFDM communication protocol, and where the transmitting module is configured to transmit the second OFDM signal over the second system bandwidth.
- the first and second OFDM signals are transmitted at a same or a different time.
- the transmitting module is configured to transmit the first OFDM signal over the non- utilized portion of the second system bandwidth if another transmission is in progress in the second system bandwidth.
- the transmitting module is further configured to, prior to transmitting the first OFDM signal, transmitting the second OFDM signal over the second system bandwidth, where the second OFDM signal is indicative of one of a transmission length, transmission time, transmission type and a channel reservation time associated with at least one of the first and second OFDM signals, and where the first OFDM signal is subsequently transmitted over the second system bandwidth.
- the second OFDM signal is transmitted using a second plurality of subcarriers having a second subcarrier frequency spacing different than the first subcarrier frequency spacing, where the second plurality of subcarriers is located in a utilized portion of the second system bandwidth.
- the second OFDM signal is transmitted using a second subset of subcarriers from the first plurality of subcarriers, different from the first subset, where the second subset being located in the utilized portion of the second system bandwidth.
- the first and second OFDM signals are generated in one of a time domain and a frequency domain, based on respective first and second predetermined OFDM signals containing data associated with the first and second OFDM communication protocols.
- the generation module is further configured to generate the first OFDM signal by mapping the first predetermined OFDM signal to subcarriers in at least the first subset and generate the second OFDM signal by mapping the second
- the second subset includes at least one subcarrier overlapping in frequency with a subcarrier of the second plurality of subcarriers.
- the generation module is further configured to generate the second predetermined OFDM signal
- the memory also contains an interpolation module configured to interpolate the second predetermined OFDM signal generated using the first plurality of subcarriers to produce an interpolated OFDM signal that can be mapped to subcarriers in the second subset.
- the first OFDM communication protocol includes an LTE protocol and the second OFDM communication protocol includes an 802.1 1 protocol.
- the first OFDM signal includes an LTE signal and the second OFDM signal includes one of a CTS frame, an STF, an LTF, and a SIG.
- the first OFDM signal is transmitted at a power level different than a power level for the second OFDM signal.
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PCT/IB2016/055181 WO2018015795A1 (en) | 2016-07-22 | 2016-08-30 | Method and system for orthogonal multi-protocol transmissions |
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US20150223075A1 (en) * | 2014-01-31 | 2015-08-06 | Intel IP Corporation | Systems, methods and devices for channel reservation |
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